EFI logo

Metadata & Repository browser

found 5 records in 125 ms.

Title: CSIRO Bushfire Team / Commonwealth Scientific and Industrial Research Organisation
Language: English
Description: CSIRO bushfire research is improving the understanding of fire, and improving technologies and strategies to save lives and limit damage. CSIRO has been involved in bushfire research for more than forty years. This has focused on: understanding and predicting bushfire behavior; the impact of bushfires on infrastructure; ecological responses to fire; the impact of climate change on bushfire risk; and pollutants and greenhouse gases as a result of bushfires.
Date:
TypeFormat:
Publisher:
Title: D2.5-1 Definition of cases to be assessed. Schedule and format of data exchange between partners /
Language: English
Description: This document is the Deliverable D2.5-1 of the research project “FIRE PARADOX”, which is co-funded by the European Commission within the 6th Framework Program (2002–2006). The document is mainly related to Work Package 2.5 “Fire effects on buildings and people”. The contents of this document mainly concern the first 18 months of the project. This is the period for which detailed planning had been carried out when the project started. It is anticipated that new ideas and needs will arise during the implementation of the project; these will be incorporated into WP2.5 as the detailed planning of the project is refined according to the administration procedure of the project.
Date:
TypeFormat:
Publisher:
Title: Deliverable D2.5-2 The effect of three-dimensionality on the building response to a forest fire /
Language: English
Description: In the practical applications of computational fluid dynamics in the prediction of the effects of forest fire on structures and people, the computational cost associated with the three dimensional simulations may sometimes restrain the usability of the simulations. Making the simulation two-dimensional reduces the computational cost by one or two orders of magnitude but may introduce additional errors to the results. In this work, the effects of the 2D assumption are studied by performing a series of simulations in both 3D and 2D, monitoring both convective and radioactive heat fluxes on the surfaces of the building surface, and reporting the difference between the 2D and 3D predictions of these heat fluxes. When doing the comparison between three- and two-dimensional simulations, special care must be taken to ensure that the two simulations actually represent the same fire scenario, which is the infinitely wide fire front. The performance of three-dimensional model at different boundary conditions and numerical parameters was first studied. The mirror boundaries on the sides of the fire front were found practical and valid for the reduction of computational cost. The grid sensitivity study performed in 2D showed that the independence of the grid resolution can be reached at 0.25 m. Due to the limited computational resources, only part of the final simulations were actually performed at this grid resolution. For the simulations of the crown fires, a coarser grid had to be used. From the viewpoint of radiation predictions, the 2D simulations were found to be better suited for the purpose than 3D simulations because in 2D, the smoothness of the radiation fields is much easier to achieve. At least 1000 angular directions were found necessary in 3D simulations. The validity of 2D simulations was studied by running a series of simulations in both 2D and 3D at different boundary conditions. The differences between the 2D and 3D simulations were studied by computing differences in convective and radioactive heat fluxes and by averaging them over the heat release rate ranges covered in the simulations. The conclusion was drawn based the cases where significant heat fluxes were found. The conclusion is that 2D simulations can be used for order-of-magnitude type of analysis, for which purpose they are well suited due to the small computing times. However, the differences seem to be too large for accurate predictions of the building and human response. Therefore, the critical simulations of the future analysis should be made in three dimensions.
Date:
TypeFormat:
Publisher:
Title: D2.5-4-36 Fire safety analysis around targets using FDS: Final achievements - Transport of firebrands and attack on buildings /
Language: English
Description: Spotting is an important mechanism of wild land fire spread. Burning particles such as twigs and leaves lofted by the buoyant plume from forest fires can be carried by ambient winds anywhere from few meters up to even a kilometre from their source. Firebrands can then start new fires far from the original fire front. This makes it difficult to predict fire-fronts movements and can cause surprising and life threatening situations for fire fighters. Firebrands also pose a significant fire hazard at Wildland-Urban Interfaces (WUI). It is possible that firebrands are even the main fire hazard at WUI locations. This study addresses the effect of firebrand attack from a forest fire on an isolated building. The effect of the firebrand attack on a house is studied at Wildland Urban Interface (WUI) conditions. Penetrations of firebrands into the house under firebrand attack as well as firebrands landing distances are studied. Fire Dynamics Simulator (FDS) [19] is used to simulate WUI fire scenarios. The results show that firebrands of all studied sizes can reach the house even across distances as large as 50 meters. The overwhelming majority of the particles reaching the house land on the roof. Few firebrands can be observed hitting the facade of the building on the side facing the fire front. Only relatively small particles were found to penetrate into the house through small openings and vents. This is attributable to the fact that smaller particles tend to follow the surrounding gas flow whereas larger particles tend to fly in parabolic trajectories and thus most probably landing on the roof or in front of the house. Compared to earlier studies on firebrand propagation, somewhat shorter propagation distances were observed. Most of the earlier studies have used some form of simple plume model or otherwise simulated a steady state flow. Results in this study suggest that the turbulence of the plume has a significant effect on the motion of firebrands. The results also suggest that for larger firebrands the propagation occurs in two distinct phases: A firebrand is lifted to high altitude by a strong updraft and is then carried further by ambient winds. A firebrand model was added to the Fire Dynamics Simulator and was used to simulate a WUI fire. While considerable uncertainties remain in modelling the fire front and the firebrand material properties, it was shown that the model can be used to investigate firebrand attacks in WUI locations.
Date:
TypeFormat:
Publisher:
Title: Deliverable 2.5-5-36 Criteria for building material ignition and for burn injuries in wildland fires: final achievements /
Language: English
Description: In fire modelling, an accurate prediction of the ignition of solid fuels requires the solution of solid- and gas-phase processes. Methods that decouple the solid from the gas phase would result in significant savings in computational cost. The work described herein presents a novel methodology for this decoupling. It is based on the observation that the time to ignition can be scaled with the square of the time integral of the incident heat flux. This relationship can be readily demonstrated for the classical solutions for time to ignition which consider constant incident heat fluxes. However, some fire applications, in particular situations of wild fires approaching the wildland-urban interface, present time-varying incident heat fluxes which render the classical solutions inaccurate. A new analytical solution for obtaining the time to ignition for ramping incident heat fluxes is presented. The proposed methodology completely decouples the solid and gas phases and is accurate in the prediction of ignition times. The methodology can be applied to both the new and classical analytical solutions. It was validated with tests carried out on PMMA and PA6. The results presented here will be useful for other teams developing forest fire models, especially the team at VTT which is working on the problem of the wildland-urban interface. The second part of the report is concerned with the development of a numerical model for the assessment of the influence of moisture migration in the severity of burn injuries affecting fire fighters. It was proven that this is an important factor affecting the severity of burn injuries. This information will constitute the basis for a research on the physiology of thermal skin burns, and will also help in the development of protective clothing for fire fighters.
Date:
TypeFormat:
Publisher: